I think it depends on what market the escort services, and also on her appearance. If she has older clients (eg: she is 40, he is 60+) who are looking for someone to take to social functions, nothing wrong with her staying in the biz. Soem guys in their 60's don't want to take a 20 year old to a function (company event, opera gala, etc) where most people are in their 60's as it will make him look like he is dating his granddaughter and attract too much attention. A date in her early 40's is a good choice as he still comes off as attracting younger women (20 years younger) but she is mature enough to not cause excessive gossip.
Also, even in incall situations sometimes it is fun to chat with an SP who has more life experience. Client can talk about his travels, SP can talk of hers. When you see escorts who are 20, they generally haven't been too many places to have common ref points. I had been all over the world by 20, but the majority haven't been at that age.
Eg:
60ish Client's businss friend: I remember in 1986 eating at the restaurant in the Eiffel Tower, and the weather outside today brings that to mind like it was yesterday.
20-year old SP: "I wasn't born yet in 1986...the Eiffel Tower, that's in Paris, right?"
43 year old SP: "Ah, Paris...my b/f and I went there in '94. We didn't eat at the tower, though we went to see it, but we did eat at that famous place where each duck order comes with a unique serial number"
Business friend: "Oh yes, the Tour D'Argent - I so enjoyed eating there...I was there with my ex-wife on our honeymoon - I saved the serial number certificate saying my duck dinner was the 800,567 one to be served since the restaurant opened in 1852. Did you have the souffle for dessert?
Sometimes age and the experience that goes with it has its advantages.
Now, if one is working at an incall agency, most retire before they are 30. I think escorts over 40 need to have a niche clientelle as indy's to do well, just my opinion. I see escorts 18-23 usually, mainly from agencies, but I am not in my 60's yet. Not sure if my taste's will change when I get older, but already friends who see me with an event-escort will say days later "You date girls who are 18? Don't you think that is a bit young for someone your age?"
Funny one (unrelated to SPs):
This wealthy out of town exec guy in his mid to late 60's comes in for a meeting and has a girl of about 19 or 20 with him. He asks an admin if she can get the girl a drink of cola, water, etc while he is in the meeting for 20 minutes. Admin (I know her) says "Do you like travelling around with your dad?" Girl says "Um, he's my husband, actually..." Admin is like "Ah...mmmm...oh..." Admin (who is 33) said she was going to ask if he was her grandfather, but thought it would be safer to go with father as that would work out to her being born when he was 47). Girl was like "Don'y worry about it - everybody makes that mistake with us haha).